The program of the Research Institute of the Hospital for Joint Diseases is devoted almost entirely to basic cancer research. These studies are carried out by the sections of Metabolism, Steroid and Leukemia Studies. The Section on Metabolism is concerned with the endocrinology of ovariectomy-induced regression of mammary cancer: (1) Studies on rat mammary tumor estradiol receptor; (2) The effects of high dose progesterone on variants of MTW9; (3) Studies on nuclear binding of estradiol receptor; (4) Estrogen receptor has enhanced affinity for BrdUrd substituted DNA; (5) cAMP-dependent protein kinases in rat mammary cancer. The Section on Steroid Studies is working on the metabolism of corticosteroids in breast tumor and prostatic tumor tissue. This section is also investigating the relationship between fetal and oncogenic development. The Section on Leukemia Studies is investigating the nature and function of glucocorticoid receptors in animal and human lymphoid cells.